Solvent extraction of epoxidized oils



United States Patent 3,254,097 SOLVENT EXTRACTION OF EPOXIDIZED OILSDavid S. Darrow, Munster, Ind., assignor to Swift & Company, Chicago,11]., a corporation of Illinois No Drawing. Filed Oct. 5, 1962, Ser. No.228,762 7 Claims. (Cl. 260--348) This invention relates to fattyepoxides and, more particularly, to improvements in the production ofoxirane-substituted higher fatty acid derivatives and to the productthereby produced.

Fatty epoxides in general have developed as an increasingly importantindustrial chemical over the last several years and it is anticipatedthat the growth of this industry will expand to an even greater extentin the near future. Esters of oxirane-substituted higher fatty acidsfind extensive use as plasticizer-stabilizers for vinyl halide resinssuch as polyvinyl chloride, polyvinylidene chloride and copolymersthereof. These esters are excellent stabilizers for vinyl halidepolymers and copolymers against heat and light degradation. In addition,because of the good compatibility of these esters with vinyl resins,plasticizing efliciency is also very favorable.

Oxirane content (percent oxirane oxygen) of a given epoxy derivativesuch. as the ester is an important criterion in the evaluation of afatty epoxide and for many uses high-oxirane or completely epoxidizedfatty acid.

derivatives are specified in order to obtain superior results.High-oxirane epoxidized glycerides. such as epoxidizednaturally-occurring glyceride oils are of considerable value inasmuch asthe high-oxirane content insures greater compatibility of the epoxidizedmaterial with vinyl resins when employed as a plasticizer. Similarly,where the epoxidized ester is used as a polymerizable material, thehigher the oxirane content the greater will be the reactivity of theepoxidized fat.

Epoxidation of naturally-occurring fatty acid esters such as animal,vegetable, and fish oils having ethylenic unsaturation usingpercarboxylic acids is a procedure well known in the art. The lowerpercarboxylic acids such as peracetic acid or performic acid arepreferred for use in the epoxidation reaction, although others such asperpropionic acid have been suggested. The peracid can be preformed orformed in situ and the reaction can be uncatalyzed or catalyzed withacidic materials such as sulfuric acid, phosphoric acid, mixtures ofthese acids, cation exchange resins in the acid form, and alkyl sulfonicacids.

The product obtained from such epoxidation reactions, while primarilyconsisting of the epoxidized fatty acid ester, usually contains someethylenic unsaturation, hydroxyl substituents and some esters which,because of the compositionof the starting material, contain saturatedfatty acids and, thus, are not epoxidized. Esters containing oleic,linoleic, and linolenic acids esterified with glycerine will contain,after epoxidation, esterified epoxy stearic acid, esterified diepoxystearic acid, and esterified triepoxy stearic acid. Nevertheless, sincenaturallyoccurring fatty materials are mixed glycerides, the epoxidationof an oil such as soybean oil will result in a mixture of individualglycerides some of which have a substantially higher percentage ofoxirane substitution than others. Those triglyceride compoundscontaining substantial saturated fatty acids will exhibit a much loweroxirane content than an epoxidized dioleyl linolein, for example. It ishighly desirable, where the product is to be employed for a specificpurpose, to concentrate the high-oxirane-substituted materials andseparate the less highly epoxidized esters and other impurities from thehigh-oxirane esters.

It is, accordingly, an object of this invention to provide a method forseparating oxirane-substituted fatty acid derivatives having ahigh-oxirane content from the low-oxirane-substituted fatty derivativesfrom a mixture containing the high-oxirane and low-oxirane materials.

Another object of the invention is to provide a method for treatingmixtures of epoxidized higher fatty acid esters by solvent extraction toprovide improved epoxidized fatty acid ester compositions.

Still another object of the invention is the provision of a method forimproving the plasticizing effectiveness of epoxidized oils with vinylresins.

Additional objects, if not specifically set forth herein, will bereadily apparent to those skilled in the art from the detaileddescription of the invention which follows.

Generally, the invention is concerned with the fractionation of mixturesof epoxidized higher fatty acid esters with an inert liquid solvent toseparate compounds having a substantial amount of oxirane substitutionfrom compounds having a lesser degree of oxirane substitution. Thesolvent employed can be one which selectively dissolves more of thehigh-oxirane compounds, leaving the compound having relatively lessoxirane substitution immiscible, or the solvent can be one whichpreferentially dissolves more of the less highly substituted oxiranecompounds. Lower oxirane-substituted oils are miscible with loweraliphatic nonpolar hydrocarbon solvents, whereas highly epoxidized oilsare not. The highly epoxidized oils, on the other hand, are misciblewith acetonitrile and methanol, whereas the less highly epoxidized oilsare not miscible with these water-soluble solvents.

More particularly, the method of this invention comprises the selectiveextraction of mixtures of epoxidized glycerides containing highlyepoxidized glycerides and less highly epoxidized glycerides to separatethe higher oxirane compounds from those of lower oxirane content. Theselective separation of these materials is achieved by mixing a solventin which either the high-oxirane or lowoxirane component ispreferentially soluble to form a twophase liquid or liquid-solid systemand separating the two phases thus formed. In this manner, a solventsolution of the high-oxirane material is'isola-ted from thesolventimmiscible, low-oxirane material or a solvent solution ofepoxidation techniques can now be prepared having a high oxirane and alow iodine value. Thus, soybean oil having an unsaturation representedby an iodine value of before epoxidation can be substantially completelyepoxidized so that the percentage of oxirane oxygen in the epoxidizedproduct is around 6.5-7%, whereas'the iodine value is generally lessthan 5 and around 1-3. Linseed oil having an iodine value beforeepoxidation of or above can be substantially completely epoxidized to anoxirane oxygen content of about 8.3-9.7 or above and a residual iodinevalue of 3-5 or less. It is possible in the case of synthetic or highlypurified triglycerides to epoxidize to an oxirane oxygen content ofaround 12%.

Even when substantially completely epoxidized, however, theseoxirane-containing triglycerides are mixtures of individualtriglycerides some of which have a high percentage of oxiranesubstitution, while others have a low percentage of oxiranesubstitution. It is possible :by the method of this invention toseparate uch mixtures into a fraction enriched in high-oxiranecompounds.

In the fractionation of the mixed glyceride ester-s, the mixture iscontacted with sufficient solvent to provide a two-phase system. Thesystem is subjected to agitation, and after the phases are allowed toseparate, the solvent solution is separated from the immiscibletfraction. In that embodiment of the invention wherein the less highlysubstituted oxirane fatty acid esters are soluble in the solvent, whilehigh-oxirane esters are immiscible, lowboiling aliphatic hydrocarbonsolvents are employed. The amount of solvent employed is that amountwhich when added to the epoxidized oil causes the formation of twophases. Because of variations in the solubility of difierent oils indifierent solvents the ratio of solvent to oil will vary. In all cases,however, enough solvent should be employed to produce two phases.Usually, a solvent to epoxidized triglyceride ratio of at least 0.5:1 issufiieient to obtain good separation, although some deviation from thisgeneral rule is apparent. At room temperature, hexane, for example, usedin a SOlVCllt-iO-Oll ratio of 0.5 :1 will not provide a two-phasesystem; whereas, isopentane used in the same amount and with the sameepoxidized ester will provide the desired two-phase system. If theamount of hexane is increased to a solvent-toepoxidized-oil ratio of1:1, two phases will appear.

Generally, the higher the solvent-to-oil ratio the better the separationand the greater the certainty of formation of two phases. Solvent-to-oilratios as high as 20:1 can be used, but increasing the ratio of solventbeyond this amount serves only to render the process less economicalwithout increasing the separation efiiciency commensu- -found verysatisfactory for eifective fractionation. Separation in some cases intotwo phases may be facilitated by chilling of the two-phase system belowroom temperature. Temperatures in the range of about 3270 F. cansometimes be employed to improve the separation. Temperaturs above roomtemperature can be employed so long as the temperature is maintainedbelow the boiling point of the solvent.

Solvent-s in which the highly epoxidized fraction of the mixed esterspreferentially soluble include methanol, acetonitrile, acrylonitrile,acetone, lower nitro paraflins rately. Solvent ratios of 05:1 through4:1 have been and an oxirane content of 8.7%.

such as nitromethane, nitroethane and nitroproipa-ne, and

dimethyl sulfoxide. Enough of any of these solvents or mixtures thereofwhen added to the mixture of epoxidized esters induces two phases; thatis, a solvent phase containing a large proportion of the highlyepoxidized material and an oil phase rich in the less highly epoxidizedmaterial. In general, any solvent in which the highly epoxidizedfraction is soluble can be employed. This solvent should also beimmiscible with nonpolar solvents such as lower aliphatic hydrocarbons.

Solvents in which the less highly epoxidized substance is preferentiallysoluble include the liquid lower aliphatic hydrocarbons, both saturatedand unsaturated, such as prolpane, the butanes, pentanes, hexanes,heptanes, and octanes. Aliphatic hydrocarbons higher in the series thanoctanes are more difficult to remove from the separated epoxy esterbecause of their generally higher boiling point and, although they canbe employed in the process, they are not recommended, if lower boilingsolvents are readily available. Hydrocarbon mixture-s containingaliphatic hydrocarbons of 5-7 carbons such as ligroin and petroleumether are very suitable for use in the method of the invention. Thesematerials have boiling points in the range of around IOU-140 F. and areliquids at atmospheric pres-sure.

The method of the invention is applicable in the treatment of a widevariety of epoxidized zfatty materials, particularly esters ofepoxidized higher fatty acids having 10-22 carbons. Included within thescope of the materials to which the invention may be applied aretriglycerides such as epoxidized animal, vegetable, and marine fats.Examples of these fats are epoxidized tallow, epoxidized soybean oil,epoxidized linseed oil, epoxidized tall oil, epoxidized safilower oil,epoxidized perilla oil, epoxidized sperm oil, epoxidized menhaden oil,and epoxidized permitted to separate into two phases.

oils when stored at room temperature for an extended period of time suchas a week or more show some sedimentation of solids or partialsolidification. If the oils are first treated by the process describedand claimed herein, this sedimentation and partial solidification isobviated. Furthermore, some untreated epoxidized oils when used at ahigh level (around 50% by weight) in plasticizing vinyl halide resinsappear to cause or induce the development of an exudate on vinyl filmsprepared from resins rplasticized with such oils. Epoxidized oilstreated in the manner described herein do not cause or promote thisdevelopment of exudate. As a result, in cases where the epoxidized oilis to be employed in combination with polyvinyl chloride orpolyvinylidene chloride or copolymers thereof, the method of theinvention can be used to substantially increase the efiectiveness of theplasticizer-stabilizer.

The following examples show the treatment of oils havingvarious oxiranecontents with various solvents. The examples are intended to beillustrative rather than limitative.

Example] 300 grams of petroleum ether was added to 300 grams ofepoxidized linseed oil having an iodine value of 8 The mixture wasagitated and then permitted to settle. The. two phases which developedwere separated in a separatory funnel and the two fractions wereanalyzed. The fraction soluble in petroleum ether contained 6.41%oxirane oxygen and had an iodine value of 7.4. The fraction-insoluble inthe petroleum ether contained 8.84% oxirane oxygen and had aniodinevalue of 9.4.

Example 11 A mixture of 300 grams of epoxidized linseed oil having aniodine value of 9.3 and an oxirane content of 8.5% was admixed with 240grams petroleum ether and 60 grams of hexane. After agitating themixture to obtain substantially complete contact of the oil with thesolvent mixture, the mix was permitted to stand, at which point the twophases separated. The portion soluble in the hydrocarbon mixturecontained 6.5% oxirane oxygen and had an iodine value of 7.4. Thatportion insoluble in the hydrocarbon solvent had 8.6% oxirane oxygen andan iodine value of 9.4. The hydrocarbon soluble portion represented 15%of the starting material.

Example III 1,000 grams of petroleum ether was added to 1,000 grams ofepoxidized linseed oil having an oxirane oxygen content of 9.08% and aniodine value of 2.33. The mixture thus formed was stirred for 3-5minutes, at which timet-he stirring was terminated and the mixture was vThe fraction soluble in the petroleum ether contained 5.82% oxiraneoxygen and had an iodine value of 1.49. The fraction which was insolublein the petroleum ether had an oxirane oxygen value of 9.59% and aniodine value of 2.43. Further treatment of the portion insoluble in thepetroleum ether (approximately 900 grams) was again extracted with 11grams additional petroleum ether. The insoluble portion derived fromthis extraction contained 9.66% oxirane oxygen and had an iodine valueof 2.4, while the portion soluble in petroleum ether had an oxiraneoxygen content of 6.34% and an iodine value of 1.66.

Example IV A highly epoxidized linseed oil having an oxirane oxygencontent of 9.73% and an iodine value of 3.98 was mixed with an equalportion of petroleum ether. The 2,000- gram mixture was agitated andthen permitted to settle. The petroleum ether soluble fraction contained6.30% oxirane oxygen and had an iodine value of 2.91.' The fractioninsoluble in petroleum ether contained 10.0% oxirane oxygen and had aniodine value of 4.1.

Example V 100 grams of epoxidized soybean oil having an oxirane oxygencontent of 7.02% and an iodine value of 3.0 was mixed with 200 grams ofisopentane. The mixture was agitated for about 35 minutes, stirring wasthen terminated, and the mixture was permitted to separate into twophases. The isopentane phase was removed and the isopentane insolubleportion was again extracted with an additional 100 gram portion ofisopentane. The isopentane extracts were combined and the solvent wasremoved by evaporation. 34 grams of highly epoxidized glycerides havingan oxirane content of 7.72% was obtained.

Example VI A mixture was formed of 85 grams of epoxidized soybean oilhaving an oxirane oxygen content of 7.02% and an iodine value of 3, and100 grams of acetonitrile. The solvent solution of the epoxidized oilwas then extracted with 100 grams of petroleum ether. The petroleumether soluble fraction was isolated and after removal of the petroleumether the product which represented about 19% of the original epoxidizedsoybean oil had an oxirane oxygen content of 5.81%. The acetonitrilesolution of the epoxidized oil was then extracted with an additional 100gram portion of petroleum ether, and after removal of the petroleumether, the residue which represented about 11% of the originalepoxidized soybean oil analyzed 5.68% oxirane oxygen.

After removal of the acetonitrile from the acetonitrile solution, theresidue which represented 60% of the original charge analyzed 7.50%oxirane oxygen. The portions soluble in petroleum ether were combinedand these materials were semisolid to solid at room temperature. Theacetonitrile soluble portion remained as a clear liquid even afterholding for one week at 40 F.

Example VI] 100 grams of epoxidized soybean oil having an oxirane oxygencontent of 7.02% and an iodine value of 3 was dissolved in 100 grams ofnitromethane. The epoxidized oil was completely miscible with thenitromethane. This solvent solution was then admixed with 100 grams ofpetroleum ether. The mixture was agitated and the petroleum etherfraction was separated from the nitromethane fraction. The residueobtained after removal of the petroleum ether weighed 11 grams andanalyzed 5.02% oxirane oxygen. An additional extraction of thenitromethane with 100 grams of petroleum ether resulted in the removalof an additional 12.5 grams of a fraction containing 5.16% oxiraneoxygen.

After removal of the nitromethane from the nitromethane fraction, '76grams of an oil having 7.53% oxirane oxygen was obtained. While thepetroleum ether soluble fractions were semisolid at room temperature,the

nitromethane soluble oil was an optically clear liquid even after fourdays at 40 F.

It will he noted that the separations in accordance with the method ofthis invention have no bearing on nor relation to the amount ofunsaturation present in the epoxidized materials. All of the startingmaterials are essentially saturated inasmuch as each has a lower iodinevalue than the well-known single-pressed stearic acid.

It is apparent that by use of the instant invention it is possible toproduce epoxidized higher fatty acid derivatives having a greaterchemical reactivity due to the higher epoxy oxygen content. Also, it ispossible to produce epoxidized higher fatty acid esters having a greatercompatibility with vinyl resins and superior heat and ultravioletstability. Again, the products of the invention do not exhibit partialsolidification or sedimentation during handling and storing.

While the invention has been described as applying particularly to thetreatment of mixtures of glyceride esters of epoxidized higher fattyacids, it can also be employed to separate mixtures of other alcoholesters of epoxidized higher fatty acids. Thus the lower aliphaticmonohydric alcohol esters of fatty acid mixtures such as those obtainedfrom epoxidized glyceride oils can also be treated to separate the highor low oxirane fractions. The methyl, ethyl, propyl, octyl esters ofepoxidized soybean, linseed, tall, or perilla oil fatty acids, forexample, can be fractionated by the method of the invention,particularly that embodiment involving the use of nitro parafiins alongwith cooling.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and, accordingly, only those limitations should *beimposed as are indicated in the appended claims.

I claim: 1. Process for treating oxirane substituted higher fattmaterials containing highly epoxidized triglycerides and less highlyepoxidized triglycerides comprising: contacting said materials with aliquid lower aliphatic hydrocar- I bon solvent in which said less highlyepoxidized materials are soluble, said solvent being selected from thegroup consisting of propane, butane, pentane, hexane, heptane, andoctane and mixtures thereof, and separating the solvent solution of saidless highly epoxidized triglycerides from the insoluble more highlyepoxidized triglycerides.

2. Process for improving the plasticizer-stabilizer properties ofepoxidized triglycerides comprising: contacting said triglycerides withan amount of a nonpolar liquid lower aliphatic hydrocarbon solventhaving a boiling point of about -140 F. and being selected from thegroup consisting of ligroin and petroleum ether sufiicient to form twophases, one comprising a solvent solution of less highly epoxidizedtriglycerides and the other phase being substantially immiscible withsaid solvent, and separating the two phases.

3. A method for improving the plasticizer-stabilizer properties ofepoxidized soybean oil comprising: contacting said epoxidized soybeanoil with an amount of nonpolar aliphatic hydrocarbon solvent selectedfrom the group consisting of propane, butane, pentane, hexane, heptane,and octane and mixtures thereof sufficient to form two phases whenadmixed with said soybean oil, one phase comprising a solvent solutionof less highly epoxidized triglycerides and the other phase beingsubstantially immiscible with said solvent, and separating the twophases.

4. A method for improving the plasticizer-stabilizer properties ofepoxidized naturally occurring triglycerides comprising: contactingnaturally occurring triglycerides with an amount of low boiling liquidnonpolar aliphatic hydrocarbon solvent selected from the groupconsisting of propane, butane, pentane, hexane, heptane, and octane andmixtures thereof suflicient to form two phases with said epoxidizedtriglycerides, one phase comprising a solvent solution of less highlyepoxidized triglycerides, the other phase being substantially immisciblewith said solvent, separating the two phases, and removing solvent fromsaid two phases.

5. A method for separating the high oxirane components from the lowoxirane components in a mixture of epoxidized triglycerides comprising:contacting said mixture with an amount of a solvent selected from thegroup consisting of methanol, acetonitrile, acrylonitrile, acetone,lower nitroparaflins, dimethyl sulfoxide, and mixtures thereof,sufiicient to dissolve said epoxidized triglycerides, adding to thesolvent solution of saidepoxidized triglycerides an amount of a nonpolaraliphatic hydrocarbon solvent selected from the group consisting ofpropane, butane, pentane, hexane, heptane, and octane and mixturesthereof sufiicient to form two solvent phases, one comprising a solventsolution of more highly epoxidized triglycerides, the other phase beingsubstantially immiscible with said solvent solution, separating the twophases and removing the solvent from each fraction.

6. Highly epoxidized glycerides substantially free of hydroxylsubstituents, sediment and other impurities, prepared in accordance withthe method of claim 5.

' 7. A method for separating the high-oxirane components from thelow-oxirane components in a mixture of epoxidized triglyceridescomprising: contacting said mixture with an amount of a first solventselected from the group consisting of methanol, acetonitrile,acrylonitrile, acetone, lower nitro parafiins, dimethyl sulfoxide, andmixtures thereof to form a solution of said triglycerides, adding anamount of a nonpolar aliphatic hydrocarbon solvent selected from thegroup consisting of propane, butane, pentane, hexane, heptane, andoctane and mixtures thereof sufficient to form two substantiallyimmiscible phases, one phase comprising a solution of References Citedby the Examiner UNITED STATES PATENTS 2,773,918 12/1956 Stephens 260-7052,798,093 7/ 1957 Stein 260-348 2,822,368 2/1958 Rowland et al 260-3482,852,558 9/1958 Feldman 260-705 2,895,966 7/1959 Ault et a1. 260-3483,041,352 6/1962 Newey 260-348 FOREIGN PATENTS 770,481 3/1957 GreatBritain. 808,955 2/ 1959 Great Britain.

2 IRVING MARCUS, Primary Examiner.

NICHOLAS S. RIZZO, WALTER A. MODANCE,

. Examiners.

1. PROCESS FOR TREATING OXIRANE SUBSTITUTED HIGHER FATTY MATERIALSCONTAINING HIGHLY EPOXIDIZED TRIGLYCERIDES AND LESS HIGHLY EPOXIDEZEDTRIGLYCERIDES COMPRISING: CONTACTING SAID MATERIALS WITH A LIQUID LOWERALIPHATIC HYDROCARBON SOLVENT IN WHICH SAID LESS HIGHLY EPOXIDIZEDMATERIALS ARE SOLUBLE, SAID SOLVENT BEING SELECTED FROM THE GROUPCONSISTING OF PROPANE, BUTANE, PENTANE, HEXANE, HEPTANE, AND OCTANE ANDMIXTURES THEREOF, AND SEPARATING THE SOLVENT SOLUTION OF SAID LESSHIGHLY EPOXIDIZED TRIGLYCERIDES FROM THE INSOLUBLE MORE HIGHLYEPOXIDIZED TRIGLYCERIDES.